Organic EL display panels which utilize organic EL to display images are used for various display devices such as mobile phones, television sets and alike. The organic EL display panels which use organic emission elements are superior in terms of ability to display high quality images and lightweight. On the other hand, it may be a problem for the organic EL display panels that the organic emission elements are likely to deteriorate because of internal heat generation in the organic EL display panels. The deterioration of the organic emission elements results in decreased luminance and a shorter life time of the organic emission elements.
There have been various proposals to overcome the drawback resulting from the internal heat generation in the organic EL display panels.
Patent Document 1 teaches endothermic materials loaded into a black matrix. Heat generated in an organic EL display panel is absorbed by the endothermic materials.
The disclosed technologies in Patent Document 1 fail to emit the heat from the inside of the organic EL display panel to the outside. Therefore, an endothermic amount depends on heat capacity of the endothermic materials. Heat exceeding the heat capacity degrades the organic emission elements. Accordingly, the technologies of Patent Document 1 are insufficient to prevent the organic emission elements from deteriorating.
Patent Documents 2 and 3 disclose technologies to use a thermally conductive layer which transmits heat generated in an organic EL display panel toward the outside of the organic EL display panel. Unlike the disclosed technologies of Patent Document 1, the thermally conductive layer facilitates to release heat in the organic EL display panel toward the outside according to the disclosed technologies of Patent Documents 2 and 3.
The disclosed technologies of Patent Document 2 and 3 require high quality of the thermally conductive layer. If the thermally conductive layer has low thermal conductivity, thermal dissipation from the organic EL display panel becomes insufficient. In general, the thermally conductive layer with high quality is expensive.
The disclosed technologies above address absorption and conduction of heat throughout an organic EL display panel.
Patent Document 1: JP 2008-77859 A
Patent Document 2: JP 2006-221875 A
Patent Document 3: JP 2006-244847 A